Use *last = nullptr;
for (Use &U : Src->uses())
last = &U;
last->getUser()->dump();
Or any better solution?
2018-04-20 19:19 GMT+02:00 Dávid Bolvanský <david.bolvansky at gmail.com>:
> Is:
>
>
> 2018-04-20 18:07 GMT+02:00 Dávid Bolvanský <david.bolvansky at
gmail.com>:
>
>> Hello,
>>
>> Code: https://godbolt.org/g/EG4Wi6
>>
>> unsigned fff3(void) {
>> char buf[10] = "";
>> return strlen(buf);
>> }
>>
>> Since we are memset-ing before strlen call, we could replace strlen
with
>> just 0.
>>
>> Has LLVM any API to get "last instruction before strlen"
which modifies
>> strlen argument "buf"? So we can check "yes, it is
memset there, replace
>> strlen with zero" ?
>>
>>
>> Thanks
>>
>
>
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Maybe nicer.. auto i = Src->uses().begin(); std::advance(i, Src->getNumUses() - 1); i->getUser()->dump(); 2018-04-20 19:19 GMT+02:00 Dávid Bolvanský <david.bolvansky at gmail.com>:> Use *last = nullptr; > for (Use &U : Src->uses()) > last = &U; > last->getUser()->dump(); > > > Or any better solution? > > 2018-04-20 19:19 GMT+02:00 Dávid Bolvanský <david.bolvansky at gmail.com>: > >> Is: >> >> >> 2018-04-20 18:07 GMT+02:00 Dávid Bolvanský <david.bolvansky at gmail.com>: >> >>> Hello, >>> >>> Code: https://godbolt.org/g/EG4Wi6 >>> >>> unsigned fff3(void) { >>> char buf[10] = ""; >>> return strlen(buf); >>> } >>> >>> Since we are memset-ing before strlen call, we could replace strlen with >>> just 0. >>> >>> Has LLVM any API to get "last instruction before strlen" which modifies >>> strlen argument "buf"? So we can check "yes, it is memset there, replace >>> strlen with zero" ? >>> >>> >>> Thanks >>> >> >> >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20180420/d0f4c45f/attachment.html>
This will not work if it's memory. Yu'd need to use MemorySSA or MemoryDependenceAnalysis to get the last instruction to modify a block of memory. On Fri, Apr 20, 2018 at 10:24 AM, Dávid Bolvanský via llvm-dev < llvm-dev at lists.llvm.org> wrote:> Maybe nicer.. > auto i = Src->uses().begin(); > std::advance(i, Src->getNumUses() - 1); > i->getUser()->dump(); > > 2018-04-20 19:19 GMT+02:00 Dávid Bolvanský <david.bolvansky at gmail.com>: > >> Use *last = nullptr; >> for (Use &U : Src->uses()) >> last = &U; >> last->getUser()->dump(); >> >> >> Or any better solution? >> >> 2018-04-20 19:19 GMT+02:00 Dávid Bolvanský <david.bolvansky at gmail.com>: >> >>> Is: >>> >>> >>> 2018-04-20 18:07 GMT+02:00 Dávid Bolvanský <david.bolvansky at gmail.com>: >>> >>>> Hello, >>>> >>>> Code: https://godbolt.org/g/EG4Wi6 >>>> >>>> unsigned fff3(void) { >>>> char buf[10] = ""; >>>> return strlen(buf); >>>> } >>>> >>>> Since we are memset-ing before strlen call, we could replace strlen >>>> with just 0. >>>> >>>> Has LLVM any API to get "last instruction before strlen" which modifies >>>> strlen argument "buf"? So we can check "yes, it is memset there, replace >>>> strlen with zero" ? >>>> >>>> >>>> Thanks >>>> >>> >>> >> > > _______________________________________________ > LLVM Developers mailing list > llvm-dev at lists.llvm.org > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev > >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20180420/aa90c1a2/attachment.html>